August lo, 1893] 



NATURE 



341 



is available for advertisements) and possesses a separate pagina- 

 tion, so that a student can extract for himself any entries which 

 he may require. At the end of the year the index is consoli- 

 dated, so as to form a permanent record of the progress 

 of the science during that period. The consolidation of 

 the index can be cheaply effected by an arrangement with 

 the printer to keep the type standing for twelve months, 

 when, in addition to the reference to the source of the 

 original paper, references to abstracts and reviews can 

 be incorporated. If the Physical Society would undertake 

 such a work, it is probable that the utility of the index would 

 lead to an extension of the system to other sciences also. It 

 is clear that by a cooperative arrangement between two or 

 more societies various indexes could be issued at a relatively 

 slightly increased cost. The economy is obvious : the same 

 files have to be searched but gnce, the same staff would be 

 competent to do the combined work at a cheaper rate, and 

 minor economics could be effected in stationary salary of 

 editor, &c. 



It remains to be seen whether English physicists are disposed 

 to abandon their present attitude of masterly inactivity — wait- 

 ing until, in the fulness of time. International Bureaus shall 

 step in and do the work for them. A simple scheme like the 

 above requires no deus ex machind in the shape of British 

 Association aid to set the ball rolling. 



E. Wyndham Hulme. 



44, Blenheim Terrace, N.W., July 31. 



The General Motions of the Atmosphere. 



Two cyclonic storms have occurred over the Indian region, 

 the tracks of which appeared to be suggestive of the existence 

 of very abnormal conditions in the general circulation of the 

 currents of the atmosphere. The first storm appeared over the 

 east of the Bay of Bengal, in about lat. 15° N., on May 20. 

 The centre crossed the bay on a W.N. W. track during the 

 2lst and 22nd, and appeared on the Orissa coast on the 

 23rd. Here it slowly recurved and followed a N., N. E., and 

 E. course, finally passing away on May 29 or 30 into Assam 

 and Manipur. The second storm appeared over the east of the 

 bay, also in about lat. 15° N., on June II, passed during the 

 I2th, 13th, 14th, 15th, and l6th W. N. Westward across the 

 bay, and to the centre of the Indian Peninsula. It there re- 

 curved, like its predecessor, through N. and N.E., and finally 

 into E. 



Combining the direction of movement of the two storms for 

 each twenty-four hours after movement commenced we obtain 

 the following figures : — 



1st day, 

 2nd ,, 

 3rd „ 

 4th „ 

 5'h ,, 



Direction. 

 N. 80° W. 

 N. 78° W. 

 N. 52° W. 

 N. 36° W. 

 N. 13° W. 



The following is the normal movement of storms during the 

 period May 20 and June 20, extracted from the " Handbook of 

 Cyclonic Storms in the Bay of Bengal," by combining the direc- 

 tions of motion of each storm recorded within the period : — 



Direction, 

 1st day, N. 48° W. 

 2nd ,, N. 39° W. 

 3rd ,, N. 40° W. 



4th ,, N. ss° W. 



It will be observed from this comparison that the direction 

 of movement of the two storms of May-June, 1893, disagrees 

 with the average movement of storms at this time of year. On 

 the other hand, " recurving " from a N. W. translation, through 

 a N. translation into a N.E. and E. translation is in the Indian 

 region a marked feature of the progressive motion of storms in 

 the spring and autumn months, and it hence follows that if the 

 direction of movement of cyclones is controlled by the upper 

 currents of the atmosphere, then the upper currents existing 

 over the Indian region at the end of May and during the first 

 half of June in the present year were analogous to those ordin- 

 arily prevailing over that region in the spring and autumn, and 

 were not comparable with those normally prevailing at or about 

 midsurnmer. Now, according to an hypothesis put forward by 

 the writer, there exists over this thermal equator a current of 



NO. 1241, VOL. 48] 



westerly translation, and it is within this current, or on the 

 margins thereof, that all the more important cyclones originate. 

 On the north side of the current of westerly translation air cur- 

 rents exist, movingfirst toN.W., thento N., and finally towards 

 N. E. and E. , transferring theair raised over equatorial regions (or 

 rather over the regions covered by the thermal equator) towards the 

 temperate zone. In ordinary years nearly all the storms of 

 the bay appearing between May 20 and June 20 appear to the 

 north of lat. 18°, and the great majority of them to the north 

 of lat. 20° N. At the same time the thermal equator and air- 

 current of westerly translation at midsummer covers northern 

 India, and its northern margin lies close to the Himalayan 

 range of mountains. This range obstructs any northerly move- 

 ment of cyclones, and hence the direction of motion of storms 

 is controlled by the current of westerly translation, and is to- 

 wards the west. In the spring and autumn, on the contrary, 

 the thermal equator lies over southern India, and the motion of 

 cyclones is — first westerly, within the equatorial current of 

 westerly translation, and subsequently along the curved track 

 described by the returning air. When, then, as in the present 

 case, we have occurring nearly at midsummer a direction of 

 movement of cyclones analogous to that prevailing in the spring 

 and autumn, it may not be unfair to assume that the thermal 

 equator, the return current of air from the torrid to the tem- 

 perate zone and the massive current of easterly translation over 

 the temperate zone, all lie to the southward of the positions 

 occupied by them in normal years. If this be the case in the 

 Indian region, it is conceivable that similarly anomalous con- 

 ditions prevail in other parts of the world ; and it is, perhaps, 

 possible that the exceptional weather which has prevailed over 

 the United Kingdom, and other portions of the north temperate 

 zone, may be due to the fact that the United Kingdom, &c., 

 relatively to that portion of the current of easterly translation 

 which ordinarily transports cyclones eastward has been modi- 

 fied, and that this portion of the current, and consequently the 

 path of cyclones, lie to the southward of their normal positions. • 



It is very difficult in India to accurately determine the lie of 

 the thermal equator, as it is very doubtful if temperature ob- 

 servations at the earth's surface are in themselves sufficient to 

 show the real atmospheric thermal conditions. Apparently, 

 however, the centre of the thermal equator in May runs from 

 about lat. 18' to 20° N. in long. 96° E. to lat. 25° N. in long. 

 68° E. The writer has extracted from the monthly weather 

 review the temperature (day temperature) anomalies of three 

 stations (Calcutta, Allahabad, and Lahore) lying to the north 

 and of three stations (Nagpur, Madras, and Bombay) lying to 

 the south of the line given above, and finds they are as 

 follows : — 



Northern 

 Stations. .Lahore 



("Calcutta = 



\ Allahabad 



= -4-2) . 



=-3o^=-3i 



Southern jN»2pur=- 2-4 



Stations, ^adras = + 13 



( Bombay = -o*8 



■0-6 



These observations show negative anomalies for both regions 

 but they would also appear to show, from the largeness of the 

 anomaly to the north and the smallness of the anomaly to the 

 south, that the line of greatest heat over India in May had been 

 thrown to the southward. According to the writer's views, how- 

 ever, the low latitude of the place of origin of the cyclones and 

 the subsequent curved trajectories of the storms are stronger 

 evidences of the southerly position of the tropical band of 

 westerly translation than that afforded by temperature observa- 

 tions taken at the earth's surface. W. L. Dallas. 

 Simla, India, July 2. 



Thunderbolt in Warwickshire. 



On Sunday evening, July 2, this part of Warwickshire was 

 visited by a very severe storm of thunder and lightning, accom- 

 panied by torrents of rain. After the storm had subsided, 

 about ten minutes before ten o'clock in the evening, a fireball 

 seems to have fallen in the village of Dunchurch, an occurrence 

 still rare enough to warrant its being placed on record. 



On the afternoon of July 4 I visited the garden of A. H. 

 Harrison, Esq., of Dunchurch Hall, in which an explosion 

 occurred at the time indicated, breaking off at about seventeen 

 feet from the ground a fine specimen of Wellingtonia growing on 



